Unmetered water service is (or was) common in, of all places, California's Central Valley, including the cities of Sacramento, Bakersfield, Modesto, Merced, and Lodi, legacy of the state's rather arcane (and highly nonscientific and environmentally hostile) Spanish-based water rights laws. Unsurprisingly, when meters were installed, even where billing wasn't based on usage, massive wastage through broken infrastructure was rapidly discovered, an interesting example of "what isn't measured cannot be managed".

See: <https://www.kqed.org/science/15191/california-communities-th...> and <https://www.sacbee.com/news/local/article201568164.html>

Other regions without use-metered water include parts of the UK, and Asia where the concept is called "non-revenue water (NRW)":

UK: <https://www.ofwat.gov.uk/households/your-water-bill/unmetere...>

Asia: <https://www.jstage.jst.go.jp/article/jscejer/76/7/76_III_277...> (PDF).

NRW: <https://en.wikipedia.org/wiki/Non-revenue_water>